S9.1 GI Infections Flashcards
What are some defences of the GI tract?
Saliva
Gastric acid
Bile
Colonic mucus
What is the benefit of lots of bacteria residing in the colon?
This prevents harmful bacteria competing for nutrients
What is the function of the gut microbiome (bacteria in the colon)?
The microbiome produces antimicrobial substances (SCFAs), and helps develop the newborn immune system
What are the 3 SCFAs produced by the gut microbiome?
Butyrate - energy source for colonocytes
Acetate - involved in cholesterol metabolism
Propionate - helps regulate satiety
What foods are good and bad for the microbiome?
High fibre diet is good
Sweeteners are bad
What is faecal microbiota use to treat?
Diarrhoea
Comes from donors
What are the main bacteria which cause diarrhoea/gastroenteritis?
Salmonella, Campylobacter, Shigella, E. coli, Clostridium difficile
What are the main virus’ which cause diarrhoea/gastroenteritis?
Norovirus, Rotavirus, Adenoviruses
Wha are the main parasites which cause diarrhoea/gastroenteritis?
Cryptosporidium, Giardia, Entamoeba
What is the transmission and symptoms of salmonella?
Ingesting contaminated food/water
Vomiting and diarrhoea
Outline the pathophysiology of salmonella
Enter enterocytes by endocytosis, move to submucosa where they’re taken up my macrophages
Macrophages transfer salmonella to reticuloendothelial system where they multiply causing lymphoid hyperplasia
Salmonella then re-enters gut from the liver
What is the transmission and symptoms of campylobacter infection?
Faecal-oral, contained food/water
Abdominal cramps, diarrhoea (can be bloody)
What are the complications of campylobacter?
Acute – cholecystitis
Late - Guillain-Barré syndrome
What is the treatment for campylobacter?
Fluids/electrolytes
Antibiotics for severe disease (eg bloody diarrhoea)
What is the transmission and virulence factor for Shigella?
Faecal-oral, contaminated food/water
Enterotoxins
Outline the pathophysiology of shigella
Shigella enters intestinal epithelia by endocytosis and multiplies.
Then invades neighbouring cells.
As cells die, mucosal abscesses form causing BLOODY diarrhoea
What is the transmission of enterotoxigenic E. coli?
Faecal-oral, contaminated water
Most common cause of travellers diarrhoea
Outline the pathophysiology of E. coli
Invades enterocytes and produce enterotoxins which cause hypersecretion of Cl-, so water leaves cells into gut lumen
What is the method of transmission of C. Diff?
Faecal-oral
Outline the pathophysiology of C. Diff
Spore formation
Following antibiotics, C diff can release; toxin A (enterotoxin causing excessive secretion) or toxin B (cytotoxin)
Pseudomembranous colitis is a complication of C. Diff, what is it?
Elevated yellow plaques join to form a pseudomembrane
What is the treatment for C. Diff?
Metronidazole
Vancomycin (severe)
What is the transmission and symptoms of rotavirus?
Faecal-oral
Vomiting, fever, then diarrhoea
Outline the pathophysiology of rotavirus
Cl secretion: Na then follows into lumen then water
SGLT1 disruption: less Na/glucose into enterocyte, so higher osmotic load in gut so water enters
Brush border dysfunction: causes malabsorption
What is the transmission method of nororvirus and where in the body does it infect?
Faecal-oral, person to person
Infects the small intestine and damages microvilli
What are the symptoms and treatment of norovirus?
Vomiting, diarrhoea
Fluid rehydration
What is the transmission of cryptosporidium?
Faecal-oral from contaminated water (commonly affects swimmers)
Outline the pathophysiology of cryptosporidium
Ingestion of an oocyst which causes watery diarrhoea
What is the treatment for cryptosporidium?
Fluid rehydration
What is the transmission for giardia?
Faecal-oral from contaminated water
Outline the pathophysiology of giardia
Cyst is ingested, stomach acid releases parasite from the cyst which can then damage small intestine and cause villous atrophy. Parasite can then become cyst again and repeat cycle
What is the treatment for giardia?
Antibiotics and fluid rehydration
What is a common condition which can occur following giardia treatment?
Lactose intolerance from lactase deficiency
What is the transmission for entamoeba histolytica and which people does it commonly affect?
Faecal-oral from contaminated water
Affects people in regions with poor sanitation, and MSM
Outline the pathophysiology of entamoeba
Ingestion of cysts which form trophozoites that invade mucosa (can spread to invade liver).
Cysts then pass out with faeces
What is the treatment of entamoeba?
Metronidazole
Which microorganisms can cause bloody diarrhoea?
Shigella (main)
Also campylobacter and entamoeba
